Liquid phase oxidation of halogenated ortho-xylenes

ABSTRACT

A method for the manufacture of halophthalic acid by liquid phase oxidation of halo-ortho-xylene is disclosed. The halophthalic acid may be dehydrated to form halophthalic anhydride which is useful in the synthesis of polyetherimide.

BACKGROUND OF INVENTION

This invention relates to liquid phase oxidation of halogen substitutedalkyl aromatic compounds. In particular, the invention relates to liquidphase oxidation of halo-ortho-xylene to produce halophthalic acid whichcan be dehydrated to produce halophthalic anhydride.

Liquid phase oxidation has long been used to produce dicarboxylic acidsfrom dialkyl benzenes. Of particular interest has been the oxidation ofdimethyl benzene (xylene) to phthalic acid, especially the oxidation ofpara-xylene to terephthalic acid, which is used in the production ofpolybutylene terephthalate. The liquid phase oxidation of xylene tophthalic acid requires the use of a catalyst, typically acobalt/manganese/bromine catalyst system, and is generally performed ina carboxylic acid solvent such as acetic acid. The catalyst system maybe augmented by the use of a co-catalyst such as zirconium, hafnium orcerium. Phthalic acid is an easily isolable solid, which can be filteredout of the reaction mixture.

Liquid phase oxidation, using a cobalt/manganese/bromine catalyst systemand a carboxylic acid solvent, has also been applied to halogenatedxylene with some success. The oxidation of the halogenated xylene ismore difficult than the oxidation of xylene due to presence of ahalogen, which is an electron withdrawing substituent, on the benzenering. The greater difficulty in oxidation results in a lower reactionselectivity and a larger amount of partial oxidation and side productsthan seen in the liquid phase oxidation of xylene under similarconditions. Additionally, halogenated phthalic acid is difficult toseparate from the partial oxidation and side products, even bydistillation. Thus it is clear that in order for a method of liquidphase oxidation of halogenated xylene to be commercially successful thereaction yield and the reaction selectivity must be very high.Optimally, for a useful commercial process, the reaction selectivityshould be high enough to result in only negligible amounts of partialoxidation and side products thus removing the need for isolation ofhalophthalic acid.

SUMMARY OF INVENTION

A method for the manufacture of halophthalic acid comprises forming areaction mixture comprising a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.25 to about 2 mole percent, based on the halo-ortho-xylene, of acobalt source, about 0.1 to about 1 mole percent, based on thehalo-ortho-xylene, of a manganese source, about 0.01 to about 0.1 molepercent, based on the halo-ortho-xylene, of a source of a metal selectedfrom zirconium, hafnium and mixtures thereof, and about 0.02 to about0.1 mole percent, based on the halo-ortho-xylene, of a bromide source;maintaining the reaction mixture at a pressure of at least about 1600kilopascals (Kpa) and at a temperature of about 130° C. to about 200°C.; introducing a molecular oxygen containing gas to the reactionmixture at a rate of at least about 0.5 normal m³ of gas/hour perkilogram (kg) of halo-ortho-xylene in the reaction mixture for a timesufficient to provide at least about 90 percent conversion of thehalo-ortho-xylene to halophthalic acid.

In another embodiment, a method for the manufacture of halophthalicanhydride comprises forming a reaction mixture comprising a mixture ofabout 7 to about 3 parts by weight of acetic acid to 1 part by weight ofa halo-ortho-xylene, about 0.25 to about 2 mole percent, based on saidhalo-ortho-xylene, of a cobalt source, about 0.1 to about 1 molepercent, based on said halo-ortho-xylene, of a manganese source, about0.01 to about 0.1 mole percent, based on said halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,and about 0.02 to about 0.1 mole percent, based on saidhalo-ortho-xylene, of a bromide source; maintaining said reactionmixture at a pressure of at least about 1600 Kpa and at a temperature ofabout 130° C. to about 200° C.; introducing a molecular oxygencontaining gas to the reaction mixture at a rate of at least about 0.5normal m³ of gas/kg of halo-ortho-xylene for a time sufficient toprovide at least about 90 percent conversion of said halo-ortho-xyleneto halophthalic acid with less than about 600 parts per million (ppm) ofhalophthalide; removing the acetic acid and any water formed as a resultof the reaction by distillation; and dehydrating the halophthalic acidto form halophthalic anhydride.

In another aspect, the method for the manufacture of halophthalic acidcomprises forming a reaction mixture comprising a mixture of about 7 toabout 3 parts by weight of acetic acid to 1 part by weight of ahalo-ortho-xylene, about 0.8 to about 1.2 mole percent, based on thehalo-ortho-xylene, of a cobalt source, about 0.4 to about 0.6 molepercent, based on the halo-ortho-xylene, of a manganese source, about0.04 to about 0.06 mole percent, based on the halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,and less than about 0.04 mole percent, based on the halo-ortho-xylene,of a source of bromide; maintaining the reaction mixture at a pressureof at least about 1600 Kpa and at a temperature of about 130° C. toabout 200° C.; introducing a molecular oxygen containing gas to thereaction mixture at a rate of at least about 0.5 normal m³ of gas/kg ofhalo-ortho-xylene for a time sufficient to provide at least about 90percent conversion of said halo-ortho-xylene to halophthalic acid.

In another aspect, a method for the manufacture of halophthalicanhydride comprises forming a reaction mixture comprising a mixture ofabout 7 to about 3 parts by weight of acetic acid to 1 part by weight ofa halo-ortho-xylene, about 0.8 to about 1.2 mole percent, based on saidhalo-ortho-xylene, of cobalt acetate or cobalt acetate hydrate, about0.4 to about 0.6 mole percent, based on said halo-ortho-xylene, ofmanganese acetate or manganese acetate hydrate, about 0.04 to about 0.06mole percent, based on said halo-ortho-xylene, of zirconium acetate orzirconium acetate hydrate, less than about 0.04 mole percent, based onsaid halo-ortho-xylene, of sodium bromide; maintaining said reactionmixture at a pressure of at least about 1600 Kpa and at a temperature ofabout 130° C. to about 200° C.; introducing a molecular oxygencontaining gas to said reaction mixture at a rate of at least about 0.5normal m³ of gas/kg of halo-ortho-xylene in the reaction mixture for atime sufficient to provide at least about 90 percent conversion of saidhalo-ortho-xylene to halophthalic acid; removing the acetic acid and anywater formed as a result of the reaction by distillation; separating thewater from the acetic acid and recycling the acetic acid; anddehydrating the halophthalic acid to form halophthalic anhydride.

In another embodiment, a method for the manufacture of polyetherimidecomprises forming a reaction mixture comprising a mixture of about 7 toabout 3 parts by weight of acetic acid to 1 part by weight of ahalo-ortho-xylene, about 0.25 to about 2 mole percent, based on thehalo-ortho-xylene, of a cobalt source, about 0.1 to about 1 molepercent, based on the halo-ortho-xylene, of a manganese source, about0.01 to about 0.1 mole percent, based on the halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,about 0.02 to about 0.1 mole percent, based on the halo-ortho-xylene, ofa bromide source; maintaining the reaction mixture at a pressure of atleast about 1600 KPa and at a temperature of about 130° C. to about 200°C.; introducing a molecular oxygen containing gas to the reactionmixture at a rate of at least about 0.5 normal m³ of gas/kg ofhalo-ortho-xylene for a time sufficient to provide at least about 90percent conversion of the halo-ortho-xylene to halophthalic acid withless than about 600 parts per million (ppm) of halophthalide; removingthe acetic acid and any water formed as a result of the reaction bydistillation; dehydrating the halophthalic acid to form halophthalicanhydride; reacting the halophthalic anhydride with 1,3-diaminobenzeneto form bis(halophthalimide) (II)

wherein X is a halogen; and reacting bis(halophthalimide) (II) with analkali metal salt of a dihydroxy substituted aromatic hydrocarbon havingthe formula (IV)

OH—A²OH  (IV)

wherein A² is a divalent aromatic hydrocarbon radical to form thepolyetherimide.

DETAILED DESCRIPTION

A method for the manufacture of halophthalic acid comprises forming areaction mixture comprising a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.25 to about 2 mole percent, based on the halo-ortho-xylene, of acobalt source, about 0.1 to about 1 mole percent, based on thehalo-ortho-xylene, of a manganese source, about 0.01 to about 0.1 molepercent, based on the halo-ortho-xylene, of a source of a metal selectedfrom zirconium, hafnium and mixtures thereof, and about 0.02 to about0.1 mole percent, based on the halo-ortho-xylene, of a bromide source.The reaction mixture is maintained at a pressure of at least about 1600Kpa and at a temperature of about 130° C. to about 200° C. A molecularoxygen containing gas is introduced to the reaction mixture at a rate ofat least about 0.5 normal m³ of oxygen containing gas/hour per kg ofhalo-ortho-xylene in the reaction mixture for a time sufficient toprovide at least about 90 percent conversion of the halo-ortho-xylene tohalophthalic acid. The introduction of the molecular oxygen containinggas creates an oxygen containing off gas, which preferably has an oxygenconcentration of less than about 3 percent by volume of the off gas.

Using the method for manufacture of halophthalic acid and anhydridedescribed herein, the high yield synthesis of high purity halophthalicacid and anhydride is possible on a scale employing hundreds ofkilograms of halo-ortho-xylene by liquid phase oxidation in the presenceof about 0.25 to about 2 mole percent (mol %) of a cobalt source, about0.1 to about 1 mol % of a manganese source, about 0.01 to about 0.1 mol% of a source of a metal selected from zirconium, hafnium and mixturesthereof, and about 0.02 to about 0.1 mol % of a bromide source.Applicants have discovered that in large scale liquid phase oxidationsemploying halo-ortho-xylene the amount of bromide can have a significantimpact on the amount of impurities present in the final product. The useof decreasing molar percentages of bromide result in a product, eitherhalophthalic acid or anhydride, with a decreased level of impuritiessuch as halophthalide. While the reasons for this phenomenon are notclearly understood it is contemplated that even lower levels of bromide,molar percentages less than about 0.02, may be useful in producing highpurity halophthalic acid or anhydride in even larger scale liquid phaseoxidations such as those employing thousands of kilograms ofhalo-ortho-xylene.

Halo-ortho-xylene suitable for use in the oxidation has the structure(IV)

wherein X is halogen. Preferably X is chlorine. The halogen substituentmay be in the 3 position (the 3-isomer) or in the 4 position (the4-isomer). The halo-ortho-xylene used in the liquid-phase oxidation mayalso be a mixture of the 3-isomer and the 4-isomer.

The liquid phase oxidation preferably employs acetic acid as a solventalthough other lower carboxylic acids may be employed, as readilyappreciated by one of ordinary skill in the art. In general, acetic acidwith a water content of up to about 3 percent may be employed. Typicallythe acetic acid is present in an amount of 7 to 3 parts by weight to 1part by weight of halo-ortho-xylene. Preferably the acetic acid ispresent in an amount of 5 to 3 parts by weight to 1 part by weight ofhalo-ortho-xylene.

Suitable molecular oxygen containing gases include gases or combinationsof gases which are a source of molecular oxygen (O₂), for example, 100%oxygen and mixtures of oxygen with inert gas with a sufficientconcentration of oxygen to effect oxidation. Sufficient oxygenconcentrations typically are greater than or equal to about 6% oxygen,preferably greater than or equal to about 15%, more preferably greaterthan or equal to about 20%. Clearly mixtures with greater than or equalto about 50% oxygen may also be used. As will be appreciated by one ofskill in the art, the concentration of oxygen may affect the rate of thereaction. A preferred molecular oxygen containing gas is air.

Useful cobalt, manganese, bromine, zirconium, and hafnium sources arethose sources which are soluble in acetic acid. As to the cobalt,manganese, zirconium or hafnium sources these include the metalsthemselves or any of their salts, complexes or compounds. These include,but are not limited to, acetates, citrates, stearates, napthenates,acetylacetonates, benzoylacetonates, carbonates, sulfates, bromides,chlorides, fluorides, nitrates, hydroxides, alkoxides, nitrides,triflates, hydrates of the foregoing and mixtures of the foregoing.Preferably the cobalt in the cobalt source is in a +2 or +3 oxidationstate. Preferably the manganese in the manganese source is in a +2 or +3oxidation state. Examples of bromide sources include, but are notlimited to, bromine, hydrogen bromide, a metal-bromide salt such assodium bromide and organic bromides. Examples of organic bromidesinclude tetrabromoethane, ethyl bromide, ethylene bromide, bromoform,xylyl bromide, xylylene bromide and mixtures comprising at least one ofthe organic bromides.

The mole percent (mol %) of the cobalt, manganese, zirconium, hafnium,and bromine are based on the amount of halo-ortho-xylene present at thebeginning of the reaction. The cobalt source is generally present inamounts of about 0.25 to about 2 mol %. Preferably, the cobalt source ispresent in an amount of less than about 1.2 mol %. In addition, it isalso preferable for the cobalt source to be present in an amount greaterthan or equal to about 0.5 mol %, and more preferably in an amountgreater than or equal to about 0.8 mol %. It is particularly preferredfor the amount of the cobalt source to be about 1 mol %.

The manganese source is present in amounts of about 0.1 to about 1 mol%.

Preferably, the manganese source is present in an amount of less than orequal to about 0.6 mol %. Additionally, it is also preferable for themanganese source to be present in an amount greater than or equal toabout 0.3 mol %, more preferably greater than or equal to about 0.4 mol%. In a particularly preferred embodiment, the manganese source ispresent in an amount of about 0.5 mol %.

The bromide source is generally present in amounts of about 0.02 toabout 0.1 mol %. Preferably, the amount of the bromide source is lessthan or equal to 0.8 mol %, more preferably less than or equal to about0.5 mol %, even more preferably less than or equal to 0.4 mol %, andmost preferably less than or equal to 0.3 mol %.

The zirconium source, hafnium source or mixture thereof is generallypresent in amounts of about 0.01 to about 0.1 mol %. Preferably, thezirconium source, hafnium source or mixture thereof is present in anamount less than or equal to about 0.06 mol %. Additionally it is alsopreferable for, the zirconium source, hafnium source or mixture thereofto be present in an amount greater than or equal to about 0.03 mol %,more preferably greater than 0.04 mol %. In a particularly preferredembodiment, the zirconium source, hafnium source or mixture thereof ispresent in an amount of about 0.05 mol %.

In an exemplary process, the halophthalic acid may be produced bycombining halo-ortho-xylene; the cobalt source; the manganese source;the bromine source; and the zirconium source, hafnium source or mixturethereof, in acetic acid in a reaction vessel. The reaction vessel isestablished at a pressure of greater than about 1600 Kpa at the desiredtemperature. The temperature of the reaction is typically about 130 ° C.to about 200° C., preferably about 150° C. to about 170° C., and morepreferably greater than about 160° C. The molecular oxygen containinggas is then introduced. The flow of the molecular oxygen containing gascreates an oxygen containing off gas that preferably has an oxygenconcentration of less than 3% by volume, preferably less than about 1%by volume. The oxygen concentration of the off gas may be determined byparamagnetic transduction oxygen analysis or other method known in theart. Useful flow rates are typically greater than or equal to 0.5 normalcubic meter (m³)/hour per kilogram (kg) of halo-ortho-xylene andpreferably greater than or equal to 1.0 normal cubic meter (m³)/hour perkilogram (kg) of halo-ortho-xylene. A normal cubic meter is defined ascubic meter under standard temperature and pressure condition.Preferably the reaction mixture is agitated using standard methods suchas mechanical stirring. The flow of molecular oxygen containing gas iscontinued until at least about 90% of halo-ortho-xylene has beenconverted to halophthalic acid, preferably until greater than 95% hasbeen converted. The amount of conversion achieved in the reaction canreadily be determined through the use of gas chromatography, massspectrometry or other methods known in the art. In our experience,amount of time required to reach 90% conversion of halo-ortho-xylene isabout 3 to about 6 hours.

Additionally, the method to manufacture halophthalic acid or anhydridemay include the optional step of monitoring the oxygen concentration ofthe off gas. When the oxygen concentration of the off gas exceeds about3% by volume that signals a slowing of the reaction. Once the oxygenconcentration of the off gas exceeds about 3% by volume the flow of themolecular oxygen containing gas may be modified so as to maintain theoxygen concentration of the off gas below about 5% by volume. The flowof the molecular oxygen containing gas may be modified in several ways.The molecular oxygen containing gas may be diluted with an inert gas soas to decrease the oxygen concentration in the molecular oxygencontaining gas, the flow rate of the molecular oxygen containing gas maybe decreased, the source of the molecular oxygen containing gas may bechanged so as to employ a molecular oxygen containing gas with a loweroxygen concentration or these methods may be combined so as to maintainthe oxygen concentration of the off gas below about 5% by volume. Themodified flow of molecular oxygen containing gas may then be continueduntil at least about 90% of halo-ortho-xylene has been converted tohalophthalic acid, preferably until greater than 95% has been converted.The amount of conversion achieved in the reaction can readily bedetermined through the use of gas chromatography, mass spectrometry orother methods known in the art.

After the reaction reaches the desired level of completion, thehalophthalic acid may be recovered as halophthalic acid or halophthalicanhydride. Many applications such as pharmaceutical applications andpolymer synthesis require halophthalic acid and halophthalic anhydridewith a high degree of purity. Such high degree of purity may be achievedby the method described herein. In fact, halophthalic acid andhalophthalic anhydride containing less than about 600 ppm ofhalophthalide, preferably less than about 500 ppm of halophthalide, andmore preferably less than about 400 ppm of halophthalide is readilyachievable. Additionally, chlorophthalic acid and chlorophthalicanhydride containing less than about 1% by weight of phthalic anhydrideand chlorobenzoic acid may also be achieved. Chlorotoluic acids anddichlorophthalic acids are typically not detected.

Most of the,acetic acid as well as water produced in the reaction can beremoved by distillation at approximately atmospheric pressure, typicallyby heating to about 200° C. at 200 Kpa. The acetic acid and water areremoved as a vapor and condensed. The water may then be removed from theacetic acid and the acetic acid may be recycled. Some dehydration of thehalophthalic acid to form halophthalic anhydride may occursimultaneously with the removal of acetic acid and water. Furthermore,the removal of acetic acid and water may be combined with dehydration toform a single step. Dehydration is typically done thermally bydistillation under vacuum at an elevated temperature allowingdehydration and isolation of the halophthalic anhydride from anyremaining acetic acid and water to occur simultaneously. Dehydration mayalso be carried out by other chemical reactions well known to thoseskilled in the art such as treatment with acetic anhydride. Afterdistillation the halophthalic anhydride is typically greater than about95 percent, preferably greater than about 97 percent, and mostpreferably greater than about 99 percent pure. Halophthalic anhydridesof high purity are used in the synthesis of polyetherimide, a high heatengineering plastic.

Polyetherimides are high heat engineering plastics having a variety ofuses. One route for the synthesis of polyetherimides proceeds through abis(4-halophthalimide) having the following structure (I):

wherein Y is a divalent alkylene, cycloalkylene, or arylene moiety and Xis a halogen. The bis(4-halophthalimide) wherein Y is a 1,3-phenyl group(II) is particularly useful.

Bis(halophthalimide)s (I) and (II) are typically formed by thecondensation of amines, e.g., 1,3-diaminobenzene with anhydrides, e.g.,4-halophthalic anhydride (III):

Polyetherimides may be synthesized by the reaction of thebis(halophthalimide) with an alkali metal salt of a dihydroxysubstituted aromatic hydrocarbon in the presence or absence of phasetransfer catalyst. Suitable phase transfer catalysts are disclosed inU.S. Pat. No. 5,229,482, which is herein incorporated by reference.Suitable dihydroxy substituted aromatic hydrocarbons include thosehaving the formula (IV)

OH—A²OH  (IV)

wherein A² is a divalent aromatic hydrocarbon radical. Suitable A²radicals include m-phenylene, p-phenylene, 4,4′-biphenylene,4,4′-bi(3,5-dimethyl)phenylene, 2,3-bis(4-phenylene)propane and similarradicals such as those disclosed by name or formula in U.S. Pat. No.4,217,438.

The A² radical preferably has the formula (V)

 —A³—Q—A⁴—  (V)

wherein each of A³ and A⁴ is a monocyclic divalent aromatic hydrocarbonradical and Q is a bridging hydrocarbon radical in which one or twoatoms separate A³ from A⁴. The free valence bonds in formula (V) areusually in the meta or para positions of A³ and A⁴ in relation to Y. A³and A⁴ may be substituted phenylene or hydrocarbon-substitutedderivative thereof, illustrative substituents (one or more) being alkyland alkenyl. Unsubstituted phenylene radicals are preferred. Both A³ andA⁴ are preferably p-phenylene, although both may be o- or m-phenylene orone o- or m-phenylene and the other p-phenylene.

The bridging radical, Q, is one in which one or two atoms, preferablyone, separate A³ from A⁴. Illustrative radicals of this type aremethylene, cyclohexylmethylene, 2-(2,2,1)-bicycloheptylmethylene,ethylene, isopropylidene, neopentylidene, cyclohexylidene, andadamantylidene. The preferred radical of formula (IV) is2,2-bis(4-phenylene)propane radical which is derived from bisphenol Aand in which Q is isopropylidene and A³ and A⁴ are each p-phenylene.

It is clear to one of ordinary skill in the art that any impuritiespresent in the halophthalic anhydride will be carried through tosubsequent steps in the polyetherimide synthesis. The presence ofsignificant levels of impurities in subsequent steps can interfere withpolymerization and cause discoloration of the final product,polyetherimide.

All patents cited are herein incorporated by reference.

The invention is further illustrated by the following non-limitingexamples.

EXAMPLES 1-5

In a laboratory scale reactor 492 grams (g) (3.5 mol) ofchloro-ortho-xylene (a mixture of about 30% 3-chloro-ortho-xylene andabout 70% 4-chloro-ortho-xylene), 1925 g of glacial acetic acid, 8.7 g(1 mol %) of cobalt acetate tetrahydrate, 4.3 g (0.5 mol %) of manganeseacetate tetrahydrate, 1.0 g (0.06 mol %) zirconium acetate solution, 4.3g (1.5 mol %) sodium acetate and varying amounts of sodium bromide werecombined. The reactor was filled with nitrogen, pressurized to 1900 KPaand heated to about 160° C. Air was then introduced to the reactorthrough a dip tube. Initially, the off gas oxygen concentration wasgreater than 0 but less than 1 percent. The reaction mixture wasagitated throughout the reaction time. After about 3 hours the oxygenconcentration of the off gas increased to greater than 3 percent. Theflow of air was stopped. Air diluted with nitrogen so as to have an offgas oxygen concentration of about 5 percent was introduced to thereactor and the temperature of the reactor was increased to about 190°C. The flow of diluted air continued for about 1 to 3 hours.Chlorophthalic acid was determined to be present in an amount of 25 wt %based on the total weight of the reaction mixture. The majority of waterformed by the reaction and the acetic acid were removed underatmospheric distillation. The chlorophthalic acid was dehydrated and anyresidual water and acetic acid were removed under heat and reducedpressure to form chlorophthalic anhydride. Chlorophthalic anhydride wasseparated from the catalyst by distillation under vacuum at distillationtemperatures near 170° C. The isolated chlorophthalic acid was analyzedby gas chromatography. Results are shown in Table 1.

[t1]

TABLE 1 Amount of Chloro- phthalides produced Example NaBr mol % wt %ppm 1* 1.0 0.57  5700 2* 0.29 0.25  2500 3* 0.14 0.01  100 4 0.03 0.46 4600 5* 0.014 2.35 23500 *comparative examples

As can be seen by examples 1-5, chlorophthalic anhydride with very smallamounts of chlorophthalide may be produced on a laboratory scale,however the amount of bromide required is greater than 0.05 mol %.

EXAMPLES 6-10

In a pilot scale reaction 200 kilograms (kg) of chloro-ortho-xylene (amixture of 3-chloro-ortho-xylene and 4-chloro ortho-xylene), 780 kg ofacetic acid, 3.5 kg (1.0 mol %) cobalt acetate tetrahydrate, 1.75 kg(0.5 mol %) manganese acetate tetrahydrate, 0.4 kg (0.05 mol %/l)zirconium acetate solution, 1.75 kg (1.5 mol %) sodium acetate andvarying amounts of sodium bromide were combined. The amount of sodiumbromide was varied by example as shown in Table 2. The reactor wasfilled with nitrogen, pressurized to 1900 Kpa and heated to about 160°C. Air was introduced to the reactor through a dip tube at a flow rategradually increasing to 200 normal m³/h. Initially, the off gas oxygenconcentration was greater than 0 but less than 1 percent. The reactionmixture was agitated throughout the reaction time. After about 1 hour,the reaction temperature was increased to 175° C. After about 3 hoursthe off gas oxygen concentration increased to greater than 3 percent.The air flow was stopped. Air diluted with nitrogen so as to have an offgas oxygen concentration of about 5 percent was introduced into thereactor and the temperature of the reactor was increased to 190° C. Theflow of diluted air was continued for about 3 hours. Final weight of thereactor contents was consistent with high conversions of chloro-o-xylenebased on the absorption of 3 moles of O₂ to generate the diacid and twomoles of water. The majority of water formed by the reaction and theacetic acid were removed under atmospheric distillation. Thechlorophthalic acid was dehydrated and any residual water and aceticacid were removed under heat and reduced pressure to form chlorophthalicanhydride. Chlorophthalic anhydride was separated from the catalyst bydistillation under vacuum at distillation temperatures near 170° C. Theisolated chlorophthalic acid was analyzed by gas chromatography. Resultsare shown in Table 2.

[t2]

TABLE 2 Amount of Chloro- phthalides produced Example NaBr mol % (wt %)ppm  6* 1.02 5.4 54000  7* 0.14 0.24  2400  8* 0.10 0.12  1200  9 0.030.02  200 10 0.02 0.03  300 *comparative examples

As can be seen in the preceding examples it is possible to producechlorophthalic anhydride with very low levels of chlorophthalide inreactions on a large scale. The overall purity of the chlorophthalicacid produced in Examples 9 and 10 was greater than 98%.

EXAMPLE 11

In a laboratory scale reactor 40 grams (g) (284 millimole (mmol)) ofchloro-ortho-xylene (a mixture of about 30% 3-chloro-ortho-xylene andabout 70% 4-chloro-ortho-xylene), 160g of glacial acetic acid, 567milligrams (mg) (0.8 mol %/o) of cobalt acetate tetrahydrate, 349 mg(0.5 mol %) of manganese acetate tetrahydrate, 9.1 mg (0.06 mol %)zirconium acetate solution, and 91 mg of 30% solution by weight ofhydrogen bromide in acetic acid were combined. The reactor was filledwith nitrogen, pressurized to 1900 KPa and heated to about 160° C. Airwas then introduced to the reactor through a dip tube. Initially, theoff gas oxygen concentration was greater than 0 but less than 1 percent.The reaction mixture was agitated throughout the reaction time. After 1hour at 160° C. the temperature was increased to about 175° C. Afterabout 3 hours the oxygen concentration of the off gas increased togreater than 3 percent. The flow of air was stopped. Air diluted withnitrogen so as to have an off gas oxygen concentration of about 5percent was introduced to the reactor and the temperature of the reactorwas increased to about 190° C. The flow of diluted air continued forabout 1 to 3 hours. The reaction mixture was analyzed by liquidchromatography (LC) and it was found that the chlorophthalic acid wasformed with yield and impurity levels comparable to the results ofExample 2. Using the method for manufacture of halophthalic acid andanhydride described herein, the high yield synthesis of high purityhalophthalic acid and anhydride is possible on a large scale employinghundreds of kilograms of halo-ortho-xylene by liquid phase oxidation inthe presence of about 0.25 to about 2 mol % of a cobalt source, about0.1 to about 1 mol % of a manganese source, about 0.01 to about 0.1 mol% of a source of a metal selected from zirconium, hafnium and mixturesthereof, and about 0.02 to about 0.1 mol % of a bromide source.Applicants have discovered that in large scale liquid phase oxidationsemploying halo-ortho-xylene the amount of bromide can have a significantimpact on the amount of impurities present in the final product. The useof decreasing molar percentages of bromide result in either halophthalicacid or anhydride with a decreased level of impurities such ashalophthalide. While the reasons for this phenomenon are not clearlyunderstood it is contemplated that even lower levels of bromide, molarpercentages less than about 0.02, may be useful in producing high purityhalophthalic acid or anhydride in even larger scale liquid phaseoxidations such as those employing thousands of kilograms ofhalo-ortho-xylene.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing fromessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method for the manufacture of halophthalic acidcomprising: forming a reaction mixture comprising: a mixture of about 7to about 3 parts by weight of acetic acid to 1 part by weight of ahalo-ortho-xylene, about 0.25 to about 2 mole percent, based on saidhalo-ortho-xylene, of a cobalt source, about 0.1 to about 1 molepercent, based on said halo-ortho-xylene, of a manganese source, about0.01 to about 0.1 mole percent, based on said halo-ortho-xylene, of asource of a metal selected from zirconium, hafnium and mixtures thereof,about 0.02 to about 0.1 mole percent, based on said halo-ortho-xylene,of a source of bromide; maintaining said reaction mixture at a pressureof at least about 1600 Kpa and at a temperature of about 130° C. toabout 200° C.; introducing a molecular oxygen containing gas to saidreaction mixture at a rate of at least about 0.5 normal m³ of gas/kg ofhalo-ortho-xylene in said reaction mixture for a time sufficient toprovide at least about 90 percent conversion of said halo-ortho-xyleneto halophthalic acid.
 2. The method of claim 1, wherein the molecularoxygen containing gas has an oxygen concentration of greater than orequal to about 6% oxygen.
 3. The method of claim 1, wherein themolecular oxygen containing gas is air.
 4. The method of claim 1,wherein the cobalt source, manganese source, zirconium or hafniumsource, and bromide source are soluble in acetic acid.
 5. The method ofclaim 4, wherein the cobalt source comprises cobalt acetate, cobaltnapthenate, cobalt sulfate, cobalt acetylacetonate, cobaltbenzoylacetonate, cobalt bromide, cobalt carbonate, cobalt chloride,cobalt fluoride, cobalt nitrate, cobalt stearate, or a hydrate of one ofthe foregoing cobalt compounds.
 6. The method of claim 5, wherein thecobalt source comprises cobalt acetate or a hydrate of cobalt acetate.7. The method of claim 4, wherein the manganese source comprisesmanganese acetate, manganese sulfate, manganese acetylacetonate,manganese bromide, manganese carbonate, manganese chloride, manganesefluoride, or manganese nitrate, or a hydrate of one of the foregoingmanganese compounds.
 8. The method of claim 7, wherein the manganesesource comprises manganese acetate or a hydrate of manganese acetate. 9.The method of claim 4, wherein the zirconium source comprises zirconiumacetate, zirconium sulfate, zirconium citrate, zirconium fluoride,zirconium hydroxide, zirconium alkoxide, zirconium chloride, zirconiumbromide, zirconium acetylacetonate, or a hydrate of one of the foregoingzirconium compounds.
 10. The method of claim 9, wherein the zirconiumsource comprises zirconium acetate or a hydrate of zirconium acetate.11. The method of claim 4, wherein the source of hafnium compriseshafnium chloride, hafnium bromide, hafnium fluoride, hafnium iodide,hafnium nitride, hafnium sulfate, hafnium triflate, hafnium nitrate, ora hydrate of one of the foregoing hafnium compounds.
 12. The method ofclaim 11, wherein the source of hafnium comprises hafnium chloride. 13.The method of claim 4, wherein the bromide source comprises bromine,hydrogen bromide, a metal-bromide salt or an organic bromide.
 14. Themethod of claim 13, wherein the bromide source comprises sodium bromide.15. The method of claim 13, wherein the bromide source compriseshydrogen bromide.
 16. The method of claim 1, wherein the amount of thecobalt source is about 0.5 to about 1.2 mole percent, based on saidhalo-ortho-xylene.
 17. The method of claim 1, wherein the amount of themanganese source is about 0.3 to about 0.6 mole percent, based on saidhalo-ortho-xylene.
 18. The method of claim 1, wherein the amount of thesource of zirconium or hafnium is about 0.03 to about 0.06 mole percent,based on said halo-ortho-xylene.
 19. The method of claim 1, wherein theamount of the source of bromide is less than or equal to about 0.04 molepercent, based on said halo-ortho-xylene.
 20. The method of claim 1,wherein the temperature is greater than or equal to 160° C.
 21. Themethod of claim 1, wherein the conversion of said halo-ortho-xylene tochlorophthalic acid is 95 percent or greater.
 22. The method of claim 1,wherein said halo-ortho-xylene comprises the 3-isomer, the 4-isomer or amixture of 3- and 4-isomers.
 23. A method for the manufacture ofhalophthalic anhydride comprising: forming a reaction mixturecomprising: a mixture of about 7 to about 3 parts by weight of aceticacid to 1 part by weight of a halo-ortho-xylene, about 0.25 to about 2mole percent, based on said halo-ortho-xylene, of a cobalt source, about0.1 to about 1 mole percent, based on said halo-ortho-xylene, of amanganese source, about 0.01 to about 0.1 mole percent, based on saidhalo-ortho-xylene, of a source of a metal selected from zirconium,hafnium and mixtures thereof, about 0.02 to about 0.1 mole percent,based on said halo-ortho-xylene, of a bromide source; maintaining saidreaction mixture at a pressure of at least about 1600 Kpa and at atemperature of about 130° C. to about 200° C.; introducing a molecularoxygen containing gas to said reaction mixture at a rate of at leastabout 0.5 normal m³ of gas/kg of halo-ortho-xylene in said reactionmixture for a time sufficient to provide at least about 90 percentconversion of said halo-ortho-xylene to halophthalic acid with less thanabout 600 parts per million (ppm) of halophthalide; removing said aceticacid and any water formed as a result of the reaction by distillation;dehydrating said halophthalic acid to form halophthalic anhydride. 24.The method of claim 23, wherein the molecular oxygen containing gas hasan oxygen concentration of greater than or equal to about 6 percentoxygen.
 25. The method of claim 23, wherein the molecular oxygencontaining gas is air.
 26. The method of claim 23, wherein the cobaltsource, manganese source, zirconium or hafnium source and bromide sourceare soluble in acetic acid.
 27. The method of claim 26, wherein thecobalt source comprises cobalt acetate, cobalt napthenate, cobaltsulfate, cobalt acetylacetonate, cobalt benzoylacetonate, cobaltbromide, cobalt carbonate, cobalt chloride, cobalt fluoride, cobaltnitrate, cobalt stearate, or a hydrate of one of the foregoing cobaltcompounds.
 28. The method of claim 27, wherein the cobalt sourcecomprises cobalt acetate or a hydrate of cobalt acetate.
 29. The methodof claim 26, wherein the manganese source comprises manganese acetate,manganese sulfate, manganese acetylacetonate, manganese bromide,manganese carbonate, manganese chloride, manganese fluoride, manganesenitrate, or a hydrate of one of the foregoing manganese compounds. 30.The method of claim 29, wherein the manganese source of comprisesmanganese acetate or a hydrate of one of the foregoing manganesecompounds.
 31. The method of claim 26, wherein the source of zirconiumcomprises zirconium acetate, zirconium sulfate, zirconium citrate,zirconium fluoride, zirconium hydroxide, zirconium alkoxide, zirconiumchloride, zirconium bromide, zirconium acetylacetonate, or a hydrate ofone of the foregoing zirconium compounds.
 32. The method of claim 31,wherein the source of zirconium comprises zirconium acetate or a hydrateof zirconium acetate.
 33. The method of claim 26, wherein the source ofhafnium comprises hafnium chloride, hafnium bromide, hafnium fluoride,hafnium iodide, hafnium nitride, hafnium sulfate, hafnium triflate,hafnium nitrate, or a hydrate of one of the foregoing hafnium compounds.34. The method of claim 33, wherein the source of hafnium compriseshafnium chloride.
 35. The method of claim 26, wherein the source ofbromide comprises bromine, hydrogen bromide, a metal-bromide salt or anorganic bromide.
 36. The method of claim 35, wherein the source ofbromide comprises sodium bromide.
 37. The method of claim 35, whereinthe source of bromide comprises hydrogen bromide.
 38. The method ofclaim 23, wherein the amount of the cobalt source is about 0.5 to about1.2 mole percent, based on said halo-ortho-xylene.
 39. The method ofclaim 23, wherein the amount of the manganese source is about 0.3 toabout 0.6 mole percent, based on said halo-ortho-xylene.
 40. The methodof claim 23, wherein the amount of the source of zirconium or hafnium isabout 0.03 to about 0.06 mole percent, based on said halo-ortho-xylene.41. The method of claim 23, wherein the amount of the source of bromideis less than or equal to about 0.04 mole percent, based on saidhalo-ortho-xylene.
 42. The method of claim 23, wherein the amount of thesource of bromide is less than or equal to about 0.03 mole percent,based on said halo-ortho-xylene.
 43. The method of claim 23, wherein thetemperature is greater than or equal to 160° C.
 44. The method of claim23, wherein the conversion of said halo-ortho-xylene to halophthalicacid is 95 percent or greater.
 45. The method of claim 23, wherein saidhalo-ortho-xylene comprises the 3-isomer, the 4-isomer or a mixture of3- and 4-isomers.
 46. The method of claim 23, wherein said acetic acidis recycled to the reaction mixture.
 47. A method for the manufacture ofhalophthalic acid comprising: forming a reaction mixture comprising: amixture of about 7 to about 3 parts by weight of acetic acid to 1 partby weight of a halo-ortho-xylene, about 0.8 to about 1.2 mole percent,based on said halo-ortho-xylene, of a cobalt source, about 0.4 to about0.6 mole percent, based on said halo-ortho-xylene, of a source ofmanganese, about 0.04 to about 0.06 mole percent, based on saidhalo-ortho-xylene, of a source of a metal selected from zirconium,hafnium and mixtures thereof, less than about 0.04 mole percent, basedon said halo-ortho-xylene, of a bromide source; maintaining saidreaction mixture at a pressure of at least about 1600 Kpa and at atemperature of about 130° C. to about 200° C.; introducing a molecularoxygen containing gas to said reaction mixture at a rate of at leastabout 0.5 normal m³ of gas/kg of halo-ortho-xylene in said reactionmixture for a time sufficient to provide at least about 90 percentconversion of said halo-ortho-xylene to halophthalic acid.
 48. A methodfor the manufacture of halophthalic anhydride comprising: forming areaction mixture comprising: a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.8 to about 1.2 mole percent, based on said halo-ortho-xylene, ofcobalt acetate or cobalt acetate hydrate, about 0.4 to about 0.6 molepercent, based on said halo-ortho-xylene, of manganese acetate ormanganese acetate hydrate, about 0.04 to about 0.06 mole percent, basedon said halo-ortho-xylene, of zirconium acetate or zirconium acetatehydrate, less than about 0.04 mole percent, based on saidhalo-ortho-xylene, of sodium bromide; maintaining said reaction mixtureat a pressure of at least about 1600 Kpa and at a temperature of about130° C. to about 200° C.; introducing a molecular oxygen containing gasto said reaction mixture at a rate of at least about 0.5 normal m³ ofgas/kg of halo-ortho-xylene in said reaction mixture for a timesufficient to provide at least about 90 percent conversion of saidhalo-ortho-xylene to halophthalic acid; removing the acetic acid and anywater formed as a result of the reaction by distillation; separatingsaid water from said acetic acid and recycling said acetic acid;dehydrating said halophthalic acid to form halophthalic anhydride.
 49. Amethod for the manufacture of polyetherimide comprising: forming areaction mixture comprising: a mixture of about 7 to about 3 parts byweight of acetic acid to 1 part by weight of a halo-ortho-xylene, about0.25 to about 2 mole percent, based on said halo-ortho-xylene, of acobalt source, about 0.1 to about 1 mole percent, based on saidhalo-ortho-xylene, of a manganese source, about 0.01 to about 0.1 molepercent, based on said halo-ortho-xylene, of a source of a metalselected from zirconium, hafnium and mixtures thereof, about 0.02 toabout 0.1 mole percent, based on said halo-ortho-xylene, of a bromidesource; maintaining said reaction mixture at a pressure of at leastabout 1600 KPa and at a temperature of about 130° C. to about 200° C.;introducing a molecular oxygen containing gas to said reaction mixtureat a rate of at least about 0.5 normal m³ of gas/kg of halo-ortho-xylenein said reaction mixture for a time sufficient to provide at least about90 percent conversion of said halo-ortho-xylene to halophthalic acidwith less than about 600 parts per million (ppm) of halophthalide;maintaining the resultant reaction mixture at 200° C. under reducedpressure to remove, as a vapor, said acetic acid and any water formed asa result of the reaction; dehydrating said halophthalic acid to formhalophthalic anhydride; reacting said halophthalic anhydride with1,3-diaminobenzene to form bis(halophthalimide) (II)

wherein X is a halogen; and reacting bis(halophthalimide) (II) with analkali metal salt of a dihydroxy substituted aromatic hydrocarbon havingthe formula (IV) OH—A²OH  (IV) wherein A² is a divalent aromatichydrocarbon radical to form the polyetherimide.